This invention relates in general to respirating devices and in particular to a new and useful breathing apparatus humidity exchanger.
In breathing apparatus it must be ensured that the air passages of the patient do not dry out and that his heat balance is not disturbed. This risk exists particularly when the cold inspiration air is supplied to the patient through a tracheotomy tubule or through an intratracheal catheter. In these cases the rhino-pharingeal area, which normally humidifies and warms up the inspiration air, is bypassed.
In order to prevent drying and cooling, it is known to provide a ventilating air humidifier, which brings the inspiration air to a value of more than 70% relative humidity, and approximately to room temperature.
Subdivided according to the principal design, ventilating air humidifiers with humidification of the ventilating air from a water supply and by a humidity exchange from the humidified expiration air into the relatively dry inspiration air are known.
In a ventilating air humidifier with a water supply, the ventilating air is fed to the patient from an air supply through a corrugated hose. Inside this hose is arranged a folded water-carrying hose, which is connected with its connections to the water supply. The wall of the water-carrying hose is waterproof, but is permeable to water vapor. The ventilating air is conducted through the corrugated hose which surrounds the water carrying hose. It is humidified by the water passing through in vapor form. In a further development, the hose carrying the ventilating gas can be arranged in a water bag hanging around the neck of the user and connected into the ventilating gas connection to the respirator or directly from the atmosphere to the user. The ventilating hose with polytetrafluoroethylene walls extending can be a part of the water bag. Its inlet can be connected either directly to the atmosphere or to a portable container with liquid oxygen. Its outlet leads to tracheotomy tubule or to a nose catheter. It is indicated that the water supply is heated by the body heat.
A disadvantage is the relatively large water supply, whose temperature must be controlled and whose large volume close to the patient always represents a potential risk when the water supply runs out. Adequate humidification of the ventilating air or of the ventilating gas requires larger diameters for the ventilating air guide. These known ventilating air humidifers are therefore very large. Heating the inspiration air by the body temperature over the water supply is also problematic (U.S. Pat. No. 3,871,373).
Another known ventilating air humidifier for respirators with humidification from a water supply also contains a waterproof foil, which is permeable to water vapor, however, and which is charged on one side with water, while the ventilating gas to be humidified passes by on the other side charged with gas. The object of arranging the evaporation surface in a star form is to achieve a greater evaporative power. In order to further reduce the size of the ventilating air humidifier without reducing the evaporation surface and thus the evaporative power, the water vapor permeable foil is formed in a patent of addition by the walls of hollow fibers. The hollow fibers are arranged as a bundle parallel to each other in a housing. They are secured together with water-carrying and a water discharge pipe on the end faces in a packing. The water to be evaporated is supplied and discharged through the water carrying pipes. It wets the hollow fibers.
This ventilating air humidifier also depends on a relatively large water supply. The heating requires special measures (West German Patent No. 4,010,748, with the additional West German Pat. No. 2,617,985 which corresponds to U.S. Pat. No. 4,146,597).
In a known humidity exchanger in apparatus for ventilation and anesthesia, where the humidity contained in the ventilating air is separated and the separated water is evaporated into the inspiration air, the inspiration and expiration channels conducted in counterflow have a diffusion foil as a common partition so that the water contained in the expiration air in vapor form can get through the diffusion foil into the inspiration air by diffusion. In order to prevent the heat contained in the expiration air from escaping into the surrounding atmosphere, the humidity exchanger can be surrounded by a heat insulation.
Humidity exchangers of this type are very large. A sufficient water vapor passage requires a corresponding large foil surface in long inspiration and expiration channels. In order to heat the inspiration air sufficiently, the heat insulation must insulate these channels well from the atmosphere (see West German Offenlegungsschrift No. 25 29 050).